Field
Embodiments of the present disclosure generally relate to semiconductor device manufacturing, and in particular to substrate cleaning in chemical mechanical polishing.
Description of the Related Art
Chemical mechanical polishing (CMP), also known as chemical mechanical planarization, is a process typically used to fabricate integrated circuits upon a silicon wafer (or “substrate”). A CMP polishing process may remove unwanted topography and materials from a partially processed substrate to produce a planar surface upon the substrate for subsequent processing. The CMP polishing process may utilize abrasives and/or a chemically-active polishing solution (sometimes called a slurry) on one or more rotating polishing pads pressed against a surface of the substrate. A cleaning process may occur subsequent to the CMP polishing process to remove residual polishing solution and/or particulates created by polishing and remaining on the substrate. This removal may prevent defects from forming on the substrate which may be scratched or otherwise damaged from the residual polishing solution and/or particulates.
The cleaning process may include scrubbing front and back surfaces of the substrate with scrubber brushes provided with a cleaning solution. The scrubber brushes may be forced against the substrate as the substrate rotates to achieve adequate cleaning efficiency and thoroughness. The substrate is rotated by substrate rollers which receive a side edge of the substrate and impart a torque using frictional contact to the side edge from a drive system that powers the substrate rollers. Monitoring the rotation of the substrate during cleaning is accomplished by a sensor wheel which is configured to rotate passively while in frictional contact with the substrate during cleaning. Maintaining effective frictional contact between the substrate and the substrate rollers, as well as between the substrate and the sensor wheel ensures effective cleaning of the substrate and consistent cleaning between substrates. Sometimes frictional contact is compromised when the substrate rollers and the sensor wheel change over time and are exposed to the cleaning solution. New approaches are needed to maintain frictional contact, so that the substrates may be reliably rotated and moved during cleaning so that defects related to inadequate removal of particulates and/or inadequate removal or polishing solution can be avoided.